A hybrid approach for estimating the drawbead restraining force in sheet metal forming
In order to get a better part quality in sheet metal forming, the rate of the material flow intothe die cavity must be efficiently controlled. This control is made by a restraining forcesupplied either by the blankholder, the drawbeads or both. When the restraining forcerequired is too high, the use of drawbeads is necessary, although excessive deformationsmay be produced. Some others disadvantages, such as difficulties of adjustment during dietry-outs in order to determine the actual Drawbead Restraining Force (DBRF), may also beemphasized. To solve these problems and to reduce the number of die try-outs, which arevery time consuming, accurate enough drawbeads concepts are necessary.Aiming to understand the influence of the most important parameters on the DBRF and toestablish a pre-estimate DBRF theory, in this study a methodology has been developedusing similitude. The data bases were achieved by Finite Element (FE) simulations done withan explicit code. Two different materials were used: A-K Steel and 2036-T4 Aluminum.The results have been compared with experimental databases of Nine(1978, 1982) and withthe analytical model of Stoughton(1988). The average of absolute error with respect toexperimental data bases was about 6 % and, for those cases studied, the maximumdiscrepancy was found to be less than 11%. For analytical ones, the average of absoluteerror was about 5 % and, for the cases studied, the maximum error was about 7%.Predictions made with this approach have a very good precision when compared withanalytical and experimental results. For this reason, it was used as a contribution forSTAMPACK®, an explicit finit element code used to simulate forming process.
Advisor:Rafael Weyler; Antonio Pedro Clapis; Jánes Landre Júnior; Laurentiu Neamtu; Márcio Bacci da Silva; Sônia Aparecida Goulart de Oliveira
School:Universidade Federal de Uberlândia
Source Type:Master's Thesis
Finite element method
Sheet metal forming
Date of Publication:07/26/2007